1. Field of the Invention
The present invention relates generally to methods and devices for treating femoral fractures. More specifically, the present invention relates to the use of novel compression hip screw and intramedullary nail assemblies with a polyaxial cross member for treating fractures to the femur.
2. Background of the Invention
There are a variety of devices used to treat femoral fractures. Fractures of the neck, head or intertrochanter of the femur have been successfully treated with a variety of compression hip screw and intramedullary nail assemblies. A common compression hip screw (CHS) assembly generally includes a side plate having a barrel member, a lag screw, and a compression screw. The side plate is secured to the exterior of the femur, and the barrel member is inserted into a predrilled hole at a proper angle in the direction of the femoral head. The lag screw, which has a threaded end and a smooth portion, is inserted through the barrel member so that it extends across the break or fracture line and into the femoral head. The threaded portion engages the femoral head. The compression screw connects the lag screw to the plate. By adjusting the tension of the compression screw, the active compression or reduction of the fracture can be adjusted. The smooth portion of the lag screw is free to slide through the barrel member to permit the adjustment of the compression screw for active compression. Furthermore, under load of a patient's body weight, while proper angulation of the femoral head is maintained, the lag screw can slide inside the barrel member to allow the fractured sides of the break to bear on each other for passive compression and optimal healing of the fracture. Some examples of CHS assemblies are the Ambi Classic compression hip screw assembly manufactured by Smith & Nephew Inc. of Memphis, Tenn., and those shown in Fixel, U.S. Pat. No. 4,432,358; Callender, Jr., U.S. Pat. No. 3,374,786; Pugh et al., U.S. Pat. No. 2,702,543; Griggs, U.S. Pat. No. 4,530,355; Blosser, U.S. Pat. No. 3,094,120; and Wagner, U.S. Pat. No. 3,842,825.
A typical intramedullary nail assembly generally includes an intramedullary rod and a cross member directed toward the femoral head. The intramedullary rod is inserted into the marrow canal of the femur. The angled cross-member is inserted through the femur and a proximal end of the intramedullary rod. Some examples of the intramedullary nail assemblies are the Russell-Taylor (RT) reconstruction nail assembly and IMHS (intramedullary hip screw) assembly manufactured by Smith & Nephew Inc. of Memphis, Tenn. A description of the IMHS assembly is in U.S. Pat. No. 5,032,125, issued on Jul. 16, 1991 to Durham et al., which is herein incorporated by reference in its entirety. As with the common CHS assembly mentioned earlier, both the RT reconstruction nail and the IMHS assemblies allow: a) active sliding compression that surgeons can apply during surgery to reduce the fracture; and b) passive sliding compression under load of a patient's body weight. While the IMHS assembly employs a barrel member similar in some ways to the barrel member in the common CHS assembly, the RT reconstruction nail relies on its own structure without any barrel to provide the active/passive sliding compression.